1. Field of the Invention
The present invention relates to a contact micro-displacement measuring apparatus applicable to high precise measurement of micro-works and hardly-measurable deep parts and productive with a low cost and high precision.
2. Description of the Related Art
Recent developments in micro-processing technologies such as micro-machining permit production of microstructures that have been impossible to produce by the conventional machining in the art and accordingly increase requirements for high precise measurement of micro-works.
In the conventional displacement measuring apparatus of contact type, however, a probe has an order-of-magnitude smaller size compared to a work to be measured and can not contact the work directly.
In addition, non-contact measuring methods such as a method using laser light are generally applied to works to which the contact measuring methods are hardly applied. The non-contact measuring methods, however, have the following problems:
(1) A spot diameter can not be adjusted easily smaller than the work; and
(2) As a light propagates in free space, they can not measure peripheries of a complicated structure that has an obstacle to shut a light path. The use of optical fibers can correspond to this problem but still remains the following problems:
(3) They require a complicated alignment among optical devices, have a low allowance over disturbance such as vibrations and temperature and moisture variations, and have a difficulty in high reliable and precise measurement; and
(4) They depend greatly on optical characteristics of the work (reflection coefficients, for example) and are of inferior general versatility.
The present invention has been made in consideration of such the problems and accordingly has an object to provide a displacement measuring apparatus, a scale member for use in the apparatus and a method of producing the scale member. The displacement measuring apparatus is efficiently productive and easily applicable to high precise measurement of displacement with contact probe detection for the above hardly-measurable works in the art such as micro-works and deep parts in complicated structures.
The present invention has another object to provide a displacement measuring apparatus using such the scale member.
According to the present invention, a scale member comprises a scale substrate; a spindle arranged in coaxial with a measurement axis for receiving a displacement input along the measurement axis; a scale displacing together with the spindle along the measurement axis; and a resilient support for supporting the spindle and scale on the scale substrate movable along the measurement axis. The spindle, scale, resilient support and scale substrate are formed integrally using fine patterning technologies.
The spindle, scale, resilient support and scale substrate may be formed integrally through photolithography and etching processes applied to a laminated substrate of Sixe2x80x94SiO2xe2x80x94Si.
In the present invention, the spindle, scale, parallel leaf spring and scale substrate may be formed in an integral structure from a laminated substrate of Sixe2x80x94SiO2xe2x80x94Si through fine patterning technologies such as photolithography and etching. Thus, a displacement measuring apparatus can be produced with a high precision for process sizes. The production using photolithography needs no mechanical alignment of the spindle and scale to the motion axis and requires relatively easy alignment to the sensor substrate. Because of micro-machining, very fine device structures can be produced. Such the micro-displacement measuring apparatus can perform high precise measurement of such parts that are hardly measured in the art.
The resilient support may comprise a parallel leaf spring coupled to the scale substrate interposing an anchor therebetween for supporting the spindle and scale in a state floating from the scale substrate.
Preferably, the scale substrate has a groove or a notch formed in the proximity of the spindle to avoid sticking during and after production processes.
A displacement measuring apparatus according to the present invention comprises the above scale member and a sensor for detecting a displacement of the scale of the scale member along the measurement axis.
Preferably, the sensor may include a sensor substrate and a detecting device mounted an the sensor substrate for detecting a displacement of the scale. The scale member couples to the sensor substrate interposing a spacer therebetween so that the scale oppositely spaces a certain gap from the detecting device.
Desirably, the spacer is formed integrally with the scale member. In this case, the spacer is bonded to the sensor substrate with an anodic bonding.
The sensor may comprise an optical sensor, including a light source for providing a light illuminating the scale and a photosensitive device for optically receiving a light from the scale, to configure an optical encoder together with the scale member.
The sensor may also comprise an induced current sensor to configure an induced current encoder together with the scale member.
The sensor may further comprise an induced current sensor to configure an induced current encoder together with the scale member.
The sensor may yet further comprise a magnetic sensor to configure a magnetic encoder together with the scale member.
According to the present invention, a method of producing a scale member comprises the steps of providing a laminated substrate including a first semiconductor substrate, a sacrifice layer and a second semiconductor substrate laminated in this order: performing a photolithography and anisotropic etching to the second semiconductor substrate to form portions to be the spindle, scale and resilient support linked together and a part of the resilient support extended wider than others; and performing an isotropic etching to the sacrifice layer to remove the sacrifice layer from beneath the spindle, scale and resilient support while remaining the sacrifice layer beneath the wider extended part of the resilient support.
Desirably, the method of producing the scale member according to the present invention may further comprises the stop of forming a spacer from a part of the second semiconductor substrate through a photolithography and anisotropic etching.
Other features and advantages of the invention will be apparent from the following description of the preferred embodiments thereof.